The current Strategic Defense Initiative (SDI) architecture depends on ground based Interceptors and space based Brilliant Pebbles (PB). Since only a limited number of these systems are available for early deployment, the addition of large mumbers of credible decoys could quickly erode the ability of these systems to accomplish their missions. Therefore, it is necessary to provide a system having the capability to discriminate the decoys from the real Reentry Vehicles (RV's). Since passive and active sensors have difficulties discriminating decoys from RV's with decoys whose weights are just a few percent of the RV's, the value of an interactive system is recognized as will be apparent from the disclosures presented hereinbelow following additional background information. The present ground based and space based interceptor technologies are grouped into two basic categories, endo- or exoatmospheric weapons. The endoatmospheric vehicles depend on the ability of a passive infrared system operating within the Earth's atmosphere to provide the vehicle with adequate signal to noise in order to perform the homing and intercept of the incoming warhead. This system suffers from extensive IR seeker cooling requirements, and thus the performance will be degraded unless advanced cooling methods are developed. The exoatmospheric interceptors use IR sensors operating outside of the Earth's atmosphere which see much lower space noise backgrounds, and thus are expected to be more effective. However, while it has been demonstrated that exoatmospheric sensors can home in on and destroy moving targets in the presence of "crude penaids", it is still questionable whether passive IR sensors can discriminate threats that contain credible decoys (i.e., weights of a few percent, same size and shape, reflectivity, etc. of RV's). The use of gamma-rays have been considered for use in favorable signature applications. In the past, however, gamma-rays have not proven to be a favorable signature for most interactive discrimination applications because highly directional gamma sensors (which are needed to function in nuclear backgrounds) were not available, and the signal obtainable by conventional gamma detectors was felt by many to be too low. However, conceptual studies have determined that a very directional (to eliminate the nuclear background), highly efficient (to increase signal-to-noise) gamma-ray sensor can provide adequate signal to noise at distances of many kilometers. The gamma sensor of this type would provide the interceptor with a very accurate means of detecting RVs from decoys, because the decoys will not contain nuclear materials. IR sensors typically have discrimination K factors of around 3, while a gamma seeker discriminator is expected to have K factors of better than 5. In addition, the gamma sensor will not degrade in the stressing atmospheric heating environment of the endoatmospheric interceptor, as would an IR sensor.
The main objective of this invention is to provide a ground based (or space based) kinetic energy kill weapon equipped with a gamma-ray homing sensor/seeker that has the capability to accurately discriminate an RV from a decoy by detecting fission gammas emanating from the warhead contained within the RV.
A further object of this invention is to provide Variable Metric (V-M) transmission sensors/seekers for interceptors which are designed to utilize gamma-ray homing and Interactive Discrimination (ID) techniques.
The overall objectives of this invention are essential to meeting threats, and it is believed that the disclosed system would perform very efficiently in both the Theater Missile Defense (TMD) and Conus Global Positioning Against Limited Strike (GPALS) defense missions.